Cell Biology Terms
Cell biology studies the cell, the smallest unit of life: its parts, how it moves materials in and out, makes energy, divides and dies. These terms cover organelles, membranes, the cell cycle, cell signaling, stem cells and the cells of blood and nerves.
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A
- Active transportCell BiologyActive transport is the movement of a substance across a cell membrane against its concentration gradient, powered by energy, usually from ATP.
- ApoptosisCell BiologyApoptosis is programmed cell death, a controlled process in which a cell dismantles itself in an orderly way without harming its neighbors.
- ATPBiochemistryATP (adenosine triphosphate) is the molecule cells use as their main short-term energy carrier, releasing energy when a phosphate group is removed.
- AxonNeuroscienceAn axon is the single long projection of a neuron that carries electrical impulses away from the cell body toward other neurons, muscles or glands.
B
- B cellImmunologyA B cell is a lymphocyte, a kind of white blood cell, that produces antibodies and forms a key part of the adaptive immune system.
- BacteriumMicrobiologyA bacterium is a single-celled prokaryote with no nucleus, found in almost every habitat on Earth, including in and on the human body.
- Binary fissionMicrobiologyBinary fission is how bacteria and archaea reproduce: a cell copies its DNA, grows, and splits in the middle into two identical daughter cells.
C
- CellCell BiologyA cell is the smallest unit that can carry out all the processes of life, enclosed by a membrane and holding its own genetic material.
- Cell cycleCell BiologyThe cell cycle is the ordered series of growth, DNA copying and division stages that a cell passes through to produce two daughter cells.
- Cell differentiationStem Cell BiologyCell differentiation is the process by which an unspecialized cell becomes a specialized type, such as a neuron or muscle cell, by switching on a set of genes.
- Cell membraneCell BiologyThe cell membrane is the thin, flexible boundary of lipids and proteins that encloses every cell and controls what enters and leaves it.
- Cell wallCell BiologyA cell wall is a rigid layer outside the plasma membrane of plant, fungal, algal and most bacterial cells that gives shape and stops them bursting.
- Cellular respirationCell BiologyCellular respiration is the set of pathways by which cells break down fuel molecules such as glucose and capture the released energy as ATP.
- CentromereCell BiologyA centromere is the constricted region of a chromosome where its two sister chromatids are held together and where spindle fibers attach in cell division.
- ChloroplastCell BiologyA chloroplast is the green organelle in plant and algal cells that captures light energy and uses it to make sugars by photosynthesis.
- ChromatinCell BiologyChromatin is the complex of DNA and proteins, mainly histones, that packs a eukaryotic cell's genome into its nucleus and makes up its chromosomes.
- ChromosomeGeneticsA chromosome is a thread-like structure of DNA and protein that carries an organism's genes; most human cells hold 46 of them in 23 pairs.
- Citric acid cycleBiochemistryThe citric acid cycle is a loop of reactions in mitochondria that breaks down acetyl groups to carbon dioxide, capturing energy as NADH and FADH2.
- Crossing overGeneticsCrossing over is the exchange of matching DNA segments between paired homologous chromosomes during meiosis, creating new combinations of alleles.
- CytokineImmunologyA cytokine is a small signaling protein released by cells, especially immune cells, that changes how other cells behave, grow or respond to infection.
- CytokinesisCell BiologyCytokinesis is the last stage of cell division, in which the cytoplasm of one cell is split to form two separate daughter cells.
- CytoplasmCell BiologyThe cytoplasm is everything inside a cell's plasma membrane apart from the nucleus: the jelly-like cytosol and the structures suspended in it.
- CytoskeletonCell BiologyThe cytoskeleton is a network of protein filaments inside a cell that gives it shape, holds organelles in place and powers movement and division.
D
- DendriteNeuroscienceA dendrite is one of the short, branching extensions of a neuron that receive signals from other cells and carry them toward the cell body.
- DiffusionCell BiologyDiffusion is the net movement of molecules from a region of higher concentration to one of lower concentration, driven by their random motion.
- DiploidGeneticsDiploid describes a cell or organism with two complete sets of chromosomes, one inherited from each parent, as in most human body cells.
- DNA replicationMolecular BiologyDNA replication is how a cell copies all of its DNA before it divides, so that each daughter cell receives a complete genome.
E
- Electron transport chainBiochemistryThe electron transport chain is a series of membrane proteins that pass electrons to oxygen and use the energy released to pump protons.
- Embryonic stem cellStem Cell BiologyAn embryonic stem cell is a pluripotent stem cell taken from the inner cell mass of an early embryo, the blastocyst, and able to form every type of body cell.
- EndocytosisCell BiologyEndocytosis is how a cell brings material in from outside: its membrane folds inward around the material and pinches off to form a vesicle.
- Endoplasmic reticulumCell BiologyThe endoplasmic reticulum is a network of membrane sacs and tubes in eukaryotic cells that makes and processes proteins and lipids.
- EukaryoteCell BiologyA eukaryote is an organism whose cells keep their DNA inside a membrane-bound nucleus and contain other membrane-bound organelles.
- ExocytosisCell BiologyExocytosis is the release of substances from a cell when a membrane-bound vesicle fuses with the plasma membrane and empties its contents outside.
F
- FlagellumMicrobiologyA flagellum is a long, whip-like projection that some cells, including many bacteria and sperm, use to swim through liquid.
- Flow cytometryImmunologyFlow cytometry is a laboratory technique for measuring the size, inner complexity and fluorescent labels of single cells as thousands stream past a laser.
G
- GameteDevelopmental BiologyA gamete is a haploid reproductive cell, such as a sperm or an egg, that fuses with a gamete of the opposite type at fertilization to form a zygote.
- Gene expressionMolecular BiologyGene expression is the use of a gene's information to make a working product, usually a protein or a functional RNA molecule.
- Glial cellNeuroscienceA glial cell is a non-neuronal cell of the nervous system that supports, insulates, feeds and protects neurons and helps regulate their signaling.
- GlycolysisBiochemistryGlycolysis is the ten-step metabolic pathway that splits one glucose molecule into two pyruvate molecules, giving a net gain of two ATP.
- Golgi apparatusCell BiologyThe Golgi apparatus is a stack of flattened membrane sacs that modifies, sorts and packages proteins and lipids sent from the endoplasmic reticulum.
H
- HaploidGeneticsHaploid describes a cell or organism that has a single set of chromosomes, such as a human egg or sperm cell with 23 chromosomes.
- HistoneMolecular BiologyA histone is a small, positively charged protein that DNA winds around to form nucleosomes, packing DNA in the nucleus and helping control gene activity.
I
L
- LipidBiochemistryA lipid is one of a varied group of biological molecules, including fats, oils, phospholipids, waxes and steroids, that do not dissolve in water.
- LysosomeCell BiologyA lysosome is a membrane-bound organelle filled with acidic digestive enzymes that break down worn-out cell parts, food particles and microbes.
M
- MacrophageImmunologyA macrophage is a large white blood cell that engulfs and digests microbes, dead cells and debris, and signals other immune cells to act.
- MeiosisCell BiologyMeiosis is a two-stage cell division that turns one diploid cell into four genetically different haploid cells, the precursors of eggs and sperm.
- Mesenchymal stem cellStem Cell BiologyA mesenchymal stem cell is a multipotent adult cell, found in bone marrow, fat and other tissues, that can turn into bone, cartilage or fat cells.
- MicrotubuleCell BiologyA microtubule is a hollow tube built from the protein tubulin, one of the main cytoskeleton fibers, used for cell shape, transport and cell division.
- MitochondrionCell BiologyA mitochondrion is a double-membraned organelle that makes most of a eukaryotic cell's ATP by breaking down fuel molecules with oxygen.
- MitosisCell BiologyMitosis is the division of a cell's nucleus that gives each of two daughter cells an identical, complete set of chromosomes.
- MorphogenDevelopmental BiologyA morphogen is a signaling molecule that spreads through developing tissue as a gradient, so cells adopt different fates depending on how much they receive.
- MyelinNeuroscienceMyelin is the fatty, layered sheath that glial cells wrap around many axons, insulating them so nerve impulses travel faster and more efficiently.
N
- NecrosisPathologyNecrosis is the unplanned death of cells or tissue caused by injury, infection, toxins or loss of blood supply, and it usually triggers inflammation.
- NeuronNeuroscienceA neuron is a nerve cell, the basic signaling unit of the nervous system, which receives information and passes it on as electrical and chemical signals.
- NondisjunctionGeneticsNondisjunction is the failure of paired chromosomes or sister chromatids to separate in cell division, leaving cells with the wrong chromosome number.
- NucleolusCell BiologyThe nucleolus is a dense region inside the nucleus, with no membrane of its own, where ribosomal RNA is made and built into ribosome subunits.
- NucleusCell BiologyThe nucleus is the membrane-bound organelle that holds a eukaryotic cell's chromosomes and controls which of its genes are used and when.
O
- OrganelleCell BiologyAn organelle is a specialized structure inside a cell, usually wrapped in its own membrane, that carries out a particular job for the cell.
- OsmosisCell BiologyOsmosis is the diffusion of water across a selectively permeable membrane, from the side with fewer dissolved solutes to the side with more.
- Oxidative phosphorylationBiochemistryOxidative phosphorylation is how cells make most of their ATP, using a proton gradient built by the electron transport chain to drive ATP synthase.
P
- PhagocytosisCell BiologyPhagocytosis is the way a cell engulfs a large particle, such as a bacterium or a dead cell, in a pocket of membrane and then digests it.
- PhospholipidBiochemistryA phospholipid is a lipid with two fatty acid tails and a head containing phosphate, and it is the main building block of all cell membranes.
- PhosphorylationBiochemistryPhosphorylation is the attachment of a phosphate group to a protein, sugar or other molecule, a key way cells make ATP and switch proteins on or off.
- PhotosynthesisBotanyPhotosynthesis is the process in which plants, algae and cyanobacteria capture light energy and store it in sugar built from carbon dioxide and water.
- PluripotencyStem Cell BiologyPluripotency is the ability of a cell to give rise to every cell type of the body, from all three germ layers, though not to a whole organism on its own.
- ProkaryoteCell BiologyA prokaryote is a usually single-celled organism, a bacterium or an archaeon, whose cell has no nucleus or other membrane-bound organelles.
R
- ReceptorPharmacologyA receptor is a protein, on a cell's surface or inside it, that binds a specific signaling molecule and triggers a response in the cell.
- Red blood cellPhysiologyA red blood cell, or erythrocyte, is a disc-shaped blood cell without a nucleus that is packed with hemoglobin and carries oxygen around the body.
- RibosomeCell BiologyA ribosome is a molecular machine of RNA and protein that reads messenger RNA and joins amino acids in the order it specifies to build a protein.
S
- SarcomerePhysiologyA sarcomere is the repeating contractile unit of striated muscle, the section of a myofibril between two Z-discs where actin and myosin interact.
- Signal transductionCell BiologySignal transduction is the chain of molecular events by which a cell turns a signal received at a receptor into a specific response inside the cell.
- Sodium–potassium pumpPhysiologyThe sodium–potassium pump is a membrane enzyme that uses ATP to move three sodium ions out of a cell and two potassium ions in on each cycle.
- Stem cellStem Cell BiologyA stem cell is an unspecialized cell that can both copy itself by dividing and give rise to specialized cell types such as blood, muscle or nerve cells.
T
- T cellImmunologyA T cell is a white blood cell that matures in the thymus and drives cell-based immunity, directing other immune cells or killing infected cells.
- TranslationMolecular BiologyTranslation is the process in which a ribosome reads the codons of a messenger RNA and links amino acids in that order to build a protein.
U
- UbiquitinCell BiologyUbiquitin is a small, highly conserved protein that cells attach to other proteins as a tag, most often to mark them for destruction.
- UnicellularCell BiologyUnicellular describes an organism whose whole body is a single cell, which carries out every life process, from feeding to reproducing, on its own.
V
- VacuoleCell BiologyA vacuole is a membrane-bound sac in a cell that stores water, nutrients or waste; most plant cells have one large central vacuole.
- VesicleCell BiologyIn cell biology, a vesicle is a small sac bounded by a membrane that carries, stores or releases materials inside a cell or across its surface.
W
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